Leakage current detection and interruption circuit

ABSTRACT

A circuit is disclosed for disconnecting a power source upon the detection of a leakage. The circuit comprises a disconnect switch for disconnecting the power source. A primary circuit controls the disconnect switch. A secondary circuit senses a leakage current. An optical switch interconnects the primary circuit and the secondary circuit for opening the disconnect switch upon the secondary circuit sensing a leakage current. The circuit is suitable for use as a leakage current detection and interruption circuit for completely electrically disconnecting and isolating the power source and the primary circuit from the secondary circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Patent Provisional applicationSer. No. 60/641,187 filed Jan. 4,2005. All subject matter set forth inprovisional application Ser. No. 60/641,187 is hereby incorporated byreference into present application as if fully Set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrical power circuit and more particularlyto a circuit for disconnecting a power source upon the detection of aleakage current.

2. Background of the Invention

Various types of electrical protective devices have been proposed by theprior art for reducing the possibility of dangerous electrical shocks aswell as the possibility of electrical fires. One general class of priorart electrical protective devices is a commonly referred to as a groundfault circuit interrupter (GFCI). A ground fault circuit interrupterdisconnects a power source upon the detection of an undesired groundingof a power line, such as by a person inadvertently being connectedbetween the power line and a ground. Other types of types of electricalprotective devices include appliance leakage current interrupters(ALCIs), equipment leakage current interrupters (ELCIs) and immersiondetection circuit interrupters (IDCIs). Underwriters Laboratories, Inc.classifies electrical protective devices as Leakage Current ProtectionDevices, in Reference Standard UL943A. The following United Statespatents are representative of leakage current protection devices of theprior art.

U.S. Pat. No. 4,131,927 to Tsuchiya, et al. discloses a current surge,normally associated with the initial application of a nominal A.C.current to an inductive load, for preventing the magnetic core of theinductive load from being driven into saturation. Initially, the currentis half wave rectified and amplitude limited. The amplitude limitationinsures that the core will not be driven into saturation. A voltagedetector connected across the inductive load senses only the counterE.M.F. of a polarity opposite to the polarity of the half wave current.When the sensed voltage reaches a predetermined value, a directconnection is provided between the A.C. supply and the inductive load,bypassing the half wave rectifier and the amplitude limiter.

U.S. Pat. No. 4,352,998 to Baker, et al. discloses a common moderejection coupler in a power switching system having a variable commonmode voltage including a first optical isolator circuit for receiving aninput signal and generating in response thereto a first signal which isnormally isolated with respect to the common mode voltage. A secondoptical isolator circuit receives the complement of the input signal andgenerates a second signal which is also normally isolated with respectto the common mode voltage. The first and second signals are thecomplement of one another. A comparator receives the first and secondsignals and generates an output signal which changes state only when thefirst and second signals complement states. Feedback control circuitryfor the comparator is provided for limiting transient changes in one ofthe first and second signals to prevent the comparator from changingoutput states when a transient change occurs in one of the first andsecond signals resulting from a change in the common mode voltage.

U.S. Pat. No. 4,424,544 to Chang, et al. discloses an optically toggledbidirectional normally-on switch with protection against bilateralvoltage and bidirectional current surges by the inclusion of a pair ofoppositely poled thyristors. One version uses a large junction-typefield-effect transistor in its main path and a pair of smallerjunction-type transistors in the subsidiary path. A photodiode arraycontrols the gate voltage on each of the transistors and turns them offwhen illuminated. A control node in the subsidiary path is connected tothe gates of the SCRs so that excess current in this path turns on theappropriately-poled thyristor to provide an additional shunt path forthe current.

U.S. Pat. No. 4,554,463 to Norbeck, et al. discloses a trigger circuitfor gating on a semiconductor switch. The power dissipated in thetrigger circuit is minimized by employing a constant current source toprovide the gate trigger current. This assures adequate triggeringregardless of supply voltage variations or switch intrinsic controlvoltage requirements. Power is saved by supplying only the currentrequired to drive the semiconductor switch on thereby preventingoverdrive. With constant d-c gate current, the precise amount of powerneeded to turn on and close the switch is provided while wastingrelatively little energy due to gate intrinsic voltage variations of theswitch or to input line voltage variations.

U.S. Pat. No. 4,717,841 to Dumortier, et al. discloses a static powerswitch circuit having a power switch member. The static power switch hasa bidirectional power switch with at least one controlled semiconductorof the thyristor or triac type with power terminals connected to an ACsource in series with a load and a circuit for controlling the powerswitch member having a first control switch whose current path isconnected to the gate of the power semiconductor through a full waverectifier bridge. This switch is connected to a circuit able to generatecontrol energy of the switch in response to an input signal.

U.S. Pat. No. 5,262,691 to Bailey, et al. discloses an apparatus forresponding to a shorted gate in a gate turnoff thyristor. The gateelectrode of which is connected by means of a controllable switch to acontrol voltage terminal having a negative potential with respect to thecathode potential of the thyristor. The controllable switch is arrangedto conduct negative gate current in response to a thyristor turnoffcommand. A voltage comparing means is coupled to the controllable switchfor detecting when the switch is conducting negative gate current ofrelatively high magnitude. Timing means is active for a predeterminedinterval following the start of the thyristor turnoff command, and logicmeans is operative to cause the switch to stop conducting negative gatecurrent if the voltage comparing means detects high gate current at theend of such interval.

U.S. Pat. No. 5,365,394 to Ibarguengoitia discloses a protectiveelectronic relay of the type which includes a feed source with aone-phase transformer, rectifying bridge, filter condenser and voltageregulator. Pickups are provided where one-phase signals are generated,connected to some diodes, connected to some capacitors and to a zenerdiode for the purpose of obtaining rectified, filtered and limitedsignals with a voltage level proportional to the line intensity of theprotected motor. A multiple microswitch connected to some resistorspermits presetting of the voltage level and nominal triggering intensityof a relay. An R-C network that can be timed in various scales comprisedof resistors a capacitor and another multiple microswitch allowsadjustment of the triggering time constant and is applied to thatvoltage level at the non-inverting input of an operational amplifierwhose inverting input is at a reference voltage. Upon the non-invertinginput of the operational amplifier reaching the reference voltage, dueto a symmetric overload, the output of the operational amplifier passesto logic state 1. This sends a positive signal to the gate of athyristor, driving it into conduction and depolarizing the base of atransistor making it pass from saturation to cut-off. As a result arelay connected to the collector of the transistor is triggered,changing the state of its contacts and causing disconnection of theprotected motor.

U.S. Pat. No. 5,418,678 to McDonald discloses an improved ground faultcircuit interrupter (GFCI) device requiring manual setting followinginitial connection to an AC power source or termination of a powersource interruption. The improved GFCI device utilizes a controlledswitching device which is responsive to a load power signal for allowingthe relay contact sets of the GFCI device to be closed only when poweris being made available at the output or load terminals. The controlledswitching device preferably comprises an opto-isolator or other type ofswitching device which provides isolation between the GFCI input andoutput terminals when the relay contact sets are open. The improved GFCIdevice may be incorporated into portable units, such as plug-in or linecord units, for use with unprotected AC receptacles.

U.S. Pat. No. 5,459,336 to Kato discloses a semiconductor photocouplercomposed of a light emitting element and a light receiving element.Wavelength of emitted light changes as a function of exciting currentintensity of the light emitting element, and capacitance of the lightreceiving element changes as a function of wavelength of receiving lightand ceases the capacity change as the receiving light disappears.Signals are transmitted in current-light-capacity type transmission withmemory action in the light receiving element.

U.S. Pat. No. 5,463,521 to Love discloses an apparatus for protectingelectronic circuit elements from hazardous voltages. The apparatusincludes a source of electrical energy that produces electrical energyhaving a predetermined energy level. An electrical load is connected tothe electrical energy source and responsively receives electricalenergy. A signaling device receives electrical energy from theelectrical energy source and produces an overvoltage signal in responseto receiving electrical energy greater than the predetermined energylevel. A NMOSFET is connected to the electrical load, and controllablyregulates the electrical current flowing through the electrical load. Acontrol device receives the overvoltage signal and responsively controlsthe operation of the NMOSFET.

U.S. Pat. No. 5,528,445 to Cooke, et al. discloses a fault currentprotection system for a traction vehicle propulsion system including asynchronous generator having armature and field windings and powerconditioning circuitry connecting the generator armature windings to atraction motor employing a normally charged capacitor which, in responseto a fault signal resulting from excess current in the generatorarmature windings, is electrically switched into parallel with theexcitation current source connected to the generator field windings soas to discharge through the generator field windings and commutate theexcitation current source.

U.S. Pat. No. 5,661,623 to McDonald, et al. discloses a ground faultcircuit interrupter (GFCI) line cord plug utilizing an electronicallylatched relay, rather than a circuit breaker or other type of mechanicallatching device, to interrupt the AC load power when a ground faultcondition occurs. In order to reduce the size of the relay and minimizethe cost and complexity of the GFCI plug, the fixed and movable relaycontact structures are mounted directly to the circuit board whichcarries the remaining components of the GFCI circuit. In a preferredembodiment, the fixed relay contact structures are integral with theplug blades of the GFCI plug. The movable relay contact structurespreferably comprise deflectable spring arms which are preloaded when therelay contacts are in the open position in order to control the contactgap, and which are deflected past the point of contact closure when therelay contacts are in the closed position in order to increase theclosing force. The principal electrical components of the GFCI plug,including the relay contacts, relay coil and sensing transformer, aremounted on the circuit board in a generally tandem or in-linearrangement in order to minimize the dimensions of the plug.

U.S. Pat. No. 6,002,563 to Esakoff, et al. discloses an improved plug-inpower module for providing a controlled amount of electrical power toone or more remote lighting fixtures or other load. The module isconfigured to sense a ground fault or other current imbalance at theload and, in response, both to trigger the module's circuit breaker toopen and to report the occurrence of such a ground fault to a centrallocation. The power module achieves these important functions withoutadding unduly to the module's complexity or size.

U.S. Pat. No. 6,218,647 to Jones discloses an ice and snow meltingsystem including at least one sensor configured for sensing atemperature or moisture associated with an ambient environment andproviding a signal indicative thereof. A heater for melting the ice andsnow includes a heater wire, a layer of insulation substantiallysurrounding the heater wire, and a conductive shield substantiallysurrounding the layer of insulation. A ground fault circuit interrupteris coupled with the shield of the heater. The ground fault circuitinterrupter detects a ground fault condition between the heater wire andthe conductive shield and provides a signal indicative thereof. Anautomatic controller is connected to the at least one sensor. Thecontroller includes heater control circuitry receiving each of thesensor signal and the ground fault circuit interrupter signal. Theheater control circuitry selectively controls operation of the heaterdependent upon the sensor signal and the ground fault circuitinterrupter signal.

U.S. Pat. No. 6,252,365 to Morris, et al. discloses a combinationcircuit breaker/motor starter including a circuit breaker trip unithaving a microprocessor and at least one removably connectable contactoror other functional module. The functional module is encoded with anidentifier, such that the microprocessor can determine the type offunctional module and appropriate configuration parameters, such as triptimes, for the particular application of the functional module. Power issupplied continuously to the trip unit during motor overload or shortcircuit conditions.

U.S. Pat. No. 6,404,265 to Guido, Jr., et al. discloses a triggercircuit for triggering a silicon device having a control terminal, wherethe silicon device is subject to variations in the intrinsic controlrequirements. The trigger circuit comprises a source of direct current(DC) supply voltage, and a DC-to-DC current mode Buck converter forconverting the supply voltage into an output DC current not subject toundesired variations due to variations in the supply voltage, the Buckconverter supplying to the control terminal a minimum current to turn onthe silicon device despite the variations in the intrinsic controlrequirements. The silicon device may comprise a silicon controlledrectifier (SCR) with a gate terminal, an anode terminal, and a cathodeterminal, and wherein the control terminal is the gate terminal, andwherein the variations in the intrinsic control requirements arevariations in the intrinsic gate-to-cathode control current and voltagerequirements.

U.S. Pat. No. 6,414,829 to Haun, et al. discloses a system for producinga simulated ground fault when arcing is present in an electricalcircuit. The system includes a sensor which monitors the electricalcircuit. An arcing fault detection circuit determines whether an arcingfault is present in response to the sensor and produces a trip signal inresponse to a determination that an arcing fault is present in theelectrical circuit. A ground fault simulator circuit produces asimulated ground fault in response to the trip signal.

U.S. Pat. No. 6,697,238 and U.S. Patent Application 20020145838 toBonilla, et al. disclose a GFCI that has secondary test switch contacts.In case closing of the primary test switch contacts fails to trip theGFCI, subsequent closing of the secondary test switch contacts resultsin a short circuit between the AC input terminals of the GFCI. The shortcircuit blows a fuse disposed on the line side of the GFCI. The blowingof the fuse disables the GFCI and/or provides an indication to the userthat the GFCI is defective.

U.S. Patent Application 20030202310 to George, et al. discloses a methodand apparatus for improving the fault protection of a monitor circuit bycoupling an input protection circuit to an output section. The inputprotection circuit may include a fusible device that limits or removes afault condition present at an input to the input protection circuit. Thefusible device may be, for example, a resettable positive temperaturecoefficient (“PTC”) device configured to limit the current passingthrough it to a predetermined level once it reaches a predeterminedtemperature. A resistive element may be thermally coupled to the PTCdevice to assist it reaching the predetermined temperature. The monitorcircuit may further be configured to generate a sensory signal inresponse to a fault condition.

U.S. Patent Application 20040037018 to Kim discloses a GFCI mis-wiringdetector including a set of input terminals for an AC source, and a setof output terminals for an AC load. The set of output terminals areconductively connected to the set of input terminals. A GFCI circuit hasone or more switches that selectively interrupt the connection betweenthe set of input terminals and the set of output terminals when a groundfault occurs. A mis-wiring detection circuit causes the one or moreswitches of the GFCI circuit to open when the AC source is electricallycoupled to the set of output terminals for a first time interval, evenif there is no imbalance in the current flow. Additionally, asuppression circuit suppresses operation of the mis-wiring detectioncircuit when the AC source is electrically coupled to the inputterminals for a second time interval. The second time interval is lessthan the first time interval.

U.S. Patent Application 20040070895 to Gershen, et al. discloses a SCR,which is used to fire a coil. The coil uses the ground conductor anddiodes as the return path to fire the coil to interrupt the voltage fromthe load. A fully shielded cord is used to detect a break in aconductor. An LED indicator in either the plug or the receptacle of theextension cord verifies that protection is available. A test button isprovided to test shield continuity and to verify proper circuitoperation.

U.S. Patent Application 20040070899 to Gershen, et al. discloses basicdetection and interruption components of an Immersion Detection CircuitInterrupter (IDCI), in combination with the line, neutral and shieldconductors of an extension or appliance cord provides a new improvedtype of detector. A Leakage Current Detector Interrupter (LCDI)interrupts current to a load when current leakage is detected betweenthe line or neutral conductors of the cord and the shield conductor. Thenew improved LCDI detector provides, either singularly or incombination, the following advantages: prevents the LCDI from beingreset should the device become inoperative (reset lockout); provides anindication of the integrity of the shield in the extension or appliancecord; tests the integrity of the shield within the extension orappliance cord, in addition to testing the functionality of the LCDI;interrupts current to the load if an electrical connection is detectedbetween the shield and neutral, or the shield and ground, in addition tothe existing detection of leakage current from the phase conductor;allows the LCDI to trip during an open neutral condition by utilizingthe ground connection as a return wire for the trip coil; and/orprovides immersion detection at the receptacle end of the extension cordin addition to protection from leakage faults.

U.S. Patent Application 20040190686 to Tidwell, et al. discloses anapparatus to determine whether or not protection circuitry for aspan-powered remote digital subscriber loop unit is properly connectedto earth ground by the deliberate assertion and detection of a groundfault from a central office line card location. The span-powered remoteunit is augmented to place a controllable conduction path in circuitwith the span-powered loop and an earth ground pin. If the earth groundpin has been properly connected to earth ground, applying the conductivepath will place a ground fault on the span, which is detected by aground fault detector within the central office line card. If the groundfault detector does not detect a ground fault in response to theapplication of the conductive path, the line card forwards a negativeground fault event message to a test center, so that a servicetechnician may be dispatched to the remote unit to correct the problem.

Therefore, it is an object of the present invention to provide a circuitfor disconnecting a power source upon the detection of a leakage currentthat provides a significant improvement in the electrical art.

Another object of this invention is to provide a circuit fordisconnecting a power source upon the detection of a leakage currentthat completely isolates the power source upon the detection of aleakage current.

Another object of this invention is to provide a circuit fordisconnecting a power source upon the detection of a leakage currentthat utilizes an optocoupler for completely isolating the power sourceupon the detection of a leakage current.

Another object of this invention is to provide a circuit fordisconnecting a power source upon the detection of a leakage currentthat requires a reduced number of electrical components.

Another object of this invention is to provide a circuit fordisconnecting a power source upon the detection of a leakage currentthat may be incorporated into existing line cord packages.

The foregoing has outlined some of the more pertinent objects of thepresent invention. These objects should be construed as being merelyillustrative of some of the more prominent features and applications ofthe invention. Many other beneficial results can be obtained bymodifying the invention within the scope of the invention. Accordinglyother objects in a full understanding of the invention may be had byreferring to the summary of the invention, the detailed descriptiondescribing the preferred embodiment in addition to the scope of theinvention defined by the claims taken in conjunction with theaccompanying drawings.

SUMMARY OF THE INVENTION

The present invention is defined by the appended claims with specificembodiments being shown in the attached drawings. For the purpose ofsummarizing the invention, the invention relates to a circuit fordisconnecting a power source upon the detection of a leakage. Thecircuit comprises a disconnect switch for disconnecting the powersource. A primary circuit is located on a primary side of the disconnectswitch for controlling the disconnect switch. A secondary circuit islocated on a secondary of the disconnect switch for sensing a leakagecurrent. An optical switch interconnects the primary circuit and thesecondary circuit for opening the disconnect switch upon the secondarycircuit sensing a leakage current.

In another embodiment of the invention, the invention comprises acircuit for disconnecting a power source upon the detection of aleakage. The circuit comprises a disconnect switch for disconnecting thepower source. A primary circuit is located on a primary side of thedisconnect switch for controlling the disconnect switch. A secondarycircuit is located on a secondary of the disconnect switch for sensing aleakage current. An optical switch interconnects the primary circuit andthe secondary circuit for opening the disconnect switch upon thesecondary circuit sensing a leakage current.

In one embodiment of the invention, the invention relates to a circuitfor disconnecting a power source upon the detection of a leakage currentfrom a wire connecting to the power source. The circuit comprises adisconnect switch interposed within the wire connecting to the powersource. A primary circuit is located on a primary side of the disconnectswitch for controlling the disconnect switch. A secondary circuit islocated on a secondary of the disconnect switch for sensing a leakagecurrent from the wire. An optical switch interconnects the primarycircuit and the secondary circuit for opening the disconnect switch uponthe secondary circuit sensing a leakage current from the wire.

In one embodiment of the invention, the invention relates to a circuitfor disconnecting a power source upon the detection of a leakage currentfrom a wire connecting to the power source. The circuit comprises adisconnect switch interposed within the wire connecting to the powersource. A primary circuit is located on a primary side of the disconnectswitch for controlling the disconnect switch. A secondary circuit islocated on a secondary of the disconnect switch for sensing a leakagecurrent from the wire. An optical switch interconnects the primarycircuit and the secondary circuit for opening the disconnect switch uponthe secondary circuit sensing a leakage current from the wire.

In one example of the invention, the disconnect switch includes asolenoid operated switch. Preferably, the disconnect switch includes anormally closed solenoid operated switch and a latch for maintaining thedisconnect switch in an open condition upon the secondary circuitsensing a leakage current from the wire. In a specific example, thelatch comprises a mechanical latch mechanism for maintaining thedisconnect switch in an open condition upon the secondary circuitsensing a leakage current from the wire.

In another example of the invention, the secondary circuit includes alight emitting device for sensing a leakage current from the wire. Thesecondary circuit may include a sensing conductor located adjacent tothe wire connected to the power source. The light emitting device sensesa leakage current between the wire and the sensing conductor. In thealternative, the secondary circuit includes a shield sensing conductorlocated about the wire connected to the power source. The light emittingdevice senses a leakage current between the wire and the shield sensingconductor.

The optical switch includes a light emitting device optically coupled toa photoconductive switch for completely electrically isolating the powersource upon the opening of the disconnect switch. The optical switchincludes a light emitting device electrically connected to the secondarycircuit for sensing a leakage current from the wire. A photoconductiveswitch is connected to the primary circuit for controlling thedisconnect switch. The light emitting device is optically coupled to aphotoconductive switch for electrically isolating the primary circuitfrom secondary circuit. In one example of the invention, the opticalswitch includes an optocoupler switch having a light emitting deviceoptically coupled to a photoconductive switch.

In still another example of the invention, the leakage current detectionand interruption circuit disconnects a power source from a loadinterconnected by a first and a second wire having a first and a secondshield, respectively, upon the detection of a leakage current betweenthe wire and the shielded of one of the first and second wires. Thecircuit comprises a disconnect switch interposed within the first andsecond wires for disconnecting the power source from the load. A primarycircuit is located between the disconnect switch and the power sourcefor controlling the disconnect switch. A secondary circuit is locatedbetween the disconnect switch and the load for sensing a leakage currentbetween the wire and the shielded of one of the first and second wires.An optical switch interconnects the primary circuit and the secondarycircuit for opening the disconnect switch upon the secondary circuitsensing a leakage current from the wire for completely electricallydisconnecting the power source from the load and completely electricallydisconnecting the primary circuit and the secondary circuit.

The foregoing has outlined rather broadly the more pertinent andimportant features of the present invention in order that the detaileddescription that follows may be better understood so that the presentcontribution to the art can be more fully appreciated. Additionalfeatures of the invention will be described hereinafter which form thesubject of the claims of the invention. It should be appreciated bythose skilled in the art that the conception and the specificembodiments disclosed may be readily utilized as a basis for modifyingor designing other structures for carrying out the same purposes of thepresent invention. It should also be realized by those skilled in theart that such equivalent constructions do not depart from the spirit andscope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be made to the following detailed description taken inconnection with the accompanying drawings in which:

FIG. 1 is an elevational view of the circuit of the present inventionconnecting a power source to a load shown as an air conditioning unit;

FIG. 2 is an enlarged view of the a portion of FIG. 1 illustrating anelectrical plug housing the circuit of the present invention;

FIG. 3 is a side view of FIG. 2;

FIG. 4 is a block diagram of the circuit of the present invention fordisconnecting an electrical power source upon the detection of a leakagecurrent;

FIG. 5 is an isometric view of a disconnect switch in a closed position;

FIG. 6 is an isometric view of the disconnect switch of FIG. 5 in anopen position;

FIG. 7 is a side sectional view of the disconnect switch of FIG. 5 inthe closed position;

FIG. 7A is a side view of the disconnect switch shown in FIG. 7;

FIG. 8 is a side sectional view of the disconnect switch of FIG. 5 in apartially open position;

FIG. 8A is a side view of the disconnect switch shown in FIG. 8;

FIG. 9 is a side sectional view of the disconnect switch of FIG. 5 in afully open position;

FIG. 9A is a side view of the disconnect switch shown in FIG. 9;

FIG. 10 is a side sectional view of the disconnect switch of FIG. 5illustrating the reset of the latch relay with the latch being in theopen position;

FIG. 10A is a side view of the disconnect switch shown in FIG. 10;

FIG. 11 is a side sectional view of the disconnect switch of FIG. 5illustrating the latch relay reset into the closed position;

FIG. 11A is a side view of the disconnect switch shown in FIG. 11;

FIG. 12 is a circuit diagram of a first embodiment of the circuit ofFIG. 4;

FIG. 13 is the circuit diagram of FIG. 12 connected to the circuit tothe power source;

FIG. 14 is the circuit diagram similar to FIG. 13 illustrating thedetection of a leakage current by the circuit;

FIG. 15 is the circuit diagram similar to FIG. 12 illustrating thedisconnection of the power source from the load;

FIG. 16 is the circuit diagram similar to FIG. 12 illustrating theoperation of a test circuit;

FIG. 17 is a circuit diagram of a second embodiment of the circuit ofFIGS. 1-4;

FIG. 18 is a circuit diagram of a third embodiment of the circuit ofFIGS. 1-4;

FIG. 19 is a circuit diagram of a fourth embodiment of the circuit ofFIGS. 1-4;

FIG. 20 is a circuit diagram of a fifth embodiment of the circuit ofFIGS. 1-4;

FIG. 21 is a circuit diagram of a sixth embodiment of the circuit ofFIGS. 1-4; and

FIG. 22 is a circuit diagram of a seventh embodiment of the circuit ofFIGS. 1-4.

Similar reference characters refer to similar parts throughout theseveral Figures of the drawings.

DETAILED DISCUSSION

FIG. 1 is an elevational view of the circuit 10 of the present inventionfor disconnecting a power source 15 upon the detection of a leakagecurrent. In this example, the power source 15 is shown as a conventionalelectrical receptacle 17. The circuit 10 is contained within a housing20 in the form of an electrical plug adapted for insertion within theconventional electrical receptacle 17. A load 30 is shown as an airconditioning unit 32 installed in a window 34. A wire assembly 40connects the circuit 10 within the housing 20 to the load 30.

FIGS. 2 and 3 are enlarged views of a portion of FIG. 1 furtherillustrating the circuit 10 contained within the housing 20. The housing20 supports conventional a first and a second electrical lug 21 and 22and a grounding lug 23 for insertion into the conventional electricalreceptacle 17. The circuit 10 connects the electrical lugs 21-23 to afirst and a second wire 41 and 42 and a grounding wire 43 of the wireassembly 40. A first and a second insulation 44 and 45 surround thefirst and second wires 41 and 42 whereas insulation 46 surrounds thegrounding wire 43 in a conventional fashion.

A first and a second shield 47 and 48 surround the first and second thefirst and second wires 41 and 42. As will be described in greater detailhereinafter, the circuit 10 disconnects the power source 15 from theload 30 upon the detection of a leakage current from any one of thefirst and second wires 41 and 42 and the first and second shields 47 and48. In addition, the circuit 10 disconnects the power source 15 from theload 30 upon the detection of a leakage current from the grounding wire43 to either one of the first and second shields 47 and 48. In thealternative, a conventional non-insulated wire (not shown) may extendalong the first and second wires 41 and 42 and the grounding wire 43 asa sensor wire for detecting a leakage current from the either one of thefirst and second wires 41 and 42 and/or the grounding wire 43.

FIG. 4 is a block diagram of the circuit 10 of the present invention fordisconnecting an electrical power source 15 from the load 30 upon thedetection of a leakage current within the wire assembly 40. In thisexample, the electrical power source 15 is shown as a conventional 110volt alternating current (AC) power source. The first terminal 21 is theline terminal whereas the second terminal 22 is the neutral terminal.Although the electrical power source 15 has been shown as conventional110 volt alternating current (AC) power source, it should be appreciatedby those skilled in the art that the present invention may be adapted tovirtually any type of power source.

The circuit 10 comprises a disconnect switch 50 interposed within thefirst and second wires 41 and 42 for disconnecting the power source 15from the load 30. In this example, a latch 60 cooperates with thedisconnect switch 50 as will be described in greater detail hereinafter.

A primary circuit 70 is connected to the disconnect switch 50 forcontrolling the disconnect switch 50. The primary circuit 70 opens thedisconnect switch 50 upon the secondary circuit 80 sensing at leakagecurrent from one of the first and second wires 41 and 42.

A secondary circuit 80 is located between the disconnect switch 50 andthe load 30 for sensing a leakage current between the one of the firstand second wires 41 and 42 and the first and second shields 47 and 48.The secondary circuit 80 senses a leakage current between the groundingwire 43 shown in FIGS. 2 and 3 and one of the first and second shields47 and 48.

The first and second shields 47 and 48 function as shield sensingconductors for enabling the secondary circuit 80 for sensing a leakagecurrent between the one of the first and second wires 41 and 42 and thefirst and second shields 47 and 48. In the alternative, a singlenon-insulated wire may be provided as a sensing conductor as shown inFIG. 18 for sensing a leakage current from either one of the first andsecond wires 41 and 42.

An optical switch 90 interconnects the primary circuit 70 and thesecondary circuit 80 for opening the disconnect switch 50 upon thesecondary circuit 80 sensing a leakage current within the wire assembly40 for completely electrically disconnecting the power source 15 fromthe load 30 and completely electrically disconnecting the primarycircuit 70 and the secondary circuit 80.

FIGS. 5 and 6 are isometric views of an example of the disconnect switch50 of FIG. 4 shown in a closed and an open position, respectively. Inthis example, the disconnect switch 50 comprises a first and a secondswitch 51 and 52 shown as resilient relay contacts 51 and 52 mounted onresilient metallic conductors 53 and 54. The resilient metallicconductors 53 and 54 bias the first and second switches 51 and 52 intoan open position.

FIGS. 7-11 illustrate various positions of the operation of thedisconnect switch 50 and the latch 60. An insulating switch operator 55interconnects the first and second switches 51 and 52 for moving thefirst and second switches 51 and 52 in unison. The insulating switchoperator 55 includes an aperture 56 defining a shoulder 57. Thedisconnect switch 50 includes a solenoid coil 58 for operating a plunger59. The plunger 50 is located for movement adjacent to the aperture 56in the insulating switch operator 55.

In this example, the latch 60 is shown as a mechanical latch comprisinga reset button 62 having a return spring 64. The resent button 62extends from the housing 20 as shown in FIGS. 1 and 2. A latch bar 66having a latch shoulder 68 is connected to the reset button 62.

FIGS. 7 and 7A illustrate the disconnect switch 50 of FIG. 5 in theclosed position. The latch shoulder 68 of the latch bar 66 engages withthe shoulder 57 defined by the aperture of the switch operator 55. Thereturn spring 64 is selected to be stronger than the resilient metallicconductors 53 and 54 biasing the first and second switches 51 and 52into an open position. The return spring 64 retains the first and secondswitches 51 and 52 in the closed position against the urging of theresilient metallic conductors 53 and 54.

FIGS. 8 and 8A illustrate the disconnect switch 50 in a partially openposition. An electrical current through the solenoid coil 58 extends theplunger 59 to displace the latch bar 66. The plunger 59 displaces thelatch bar 66 to disengage the latch shoulder 68 of the latch bar 66 fromthe shoulder 57 of the switch operator 55. The disengagement of thelatch shoulder 68 from the shoulder 57 permits the resilient metallicconductors 53 and 54 to bias the first and second switches 51 and 52into the open position.

FIGS. 9 and 9A is a side sectional view of the disconnect switch 50 in afully open position. The resilient metallic conductors 53 and 54 urgethe first and second switches 51 and 52 into the open position. Thefirst and second switches 51 and 52 remains in the open position untilthe disconnect switch 50 is manually reset.

Concomitantly therewith, the return spring 64 moves the reset button 62into an extended position. The resent button 62 extends from the housing20 as shown in FIGS. 1 and 2. The latch bar 66 and the latch shoulder 68move in unison with the reset button 62.

FIGS. 10 and 10A illustrate the movement of the reset button 62 by anoperator to reset the disconnect switch 50. The reset button 62 isdepressed against the urging of the return spring 64. The latch shoulder68 of the latch bar 66 reengages with the shoulder 57 of the switchoperator 55.

FIGS. 11 and 11A illustrate the fully reset disconnect switch 50. Thereturn spring 64 moves the first and second switches 51 and 52 into theclosed position against the urging of the urging of the resilientmetallic conductors 53 and 54.

Although the disconnect switch 50 has been shown as a normally open,latch closed solenoid mechanism, it should be appreciated by thoseskilled in the art that various types of mechanical and or electricalswitches may be utilized within the present invention for providing thestructure and function of the disconnect switch 50.

FIG. 12 is a circuit diagram of a first embodiment of the circuit 10 ofFIG. 4. The first and second terminals 21 and 22 extending from thehousing 20 are connected to the wires 41 and 42 of the wire assembly 40.A surge suppressor shown as a metal oxide varistor 26 is connectedacross the first and second wires 41 and 42. The function and operationof the metal oxide varistor 26 should be well known to those skilled inthe art.

The disconnect switch 50 is interposed within the wire assembly 40 withthe first and second switches 51 and 52 interposed within the first andsecond wires 41 and 42. The disconnect switch 50 is shown in the closedor reset condition.

The primary circuit 70 is located on a primary side of the disconnectswitch 50 for controlling the disconnect switch 50. The primary circuit70 opens the disconnect switch 50 upon the secondary circuit 80 sensinga leakage current from one of the wire 41 and 42. The disconnect switch50 is controlled through the solenoid coil 58 by the primary circuit 70.A diode 68 providing power through the solenoid coil 58 of thedisconnect switch 50 to a conductor 69 to power the primary circuit 70.The solenoid coil 58 is connected to a voltage divider network 71comprising resistor 72 and resistor 73. A capacitor 75 is connectedacross the resistor 73 of the voltage divider network 71. The conductor69 is connected to a switch shown as a thyristor or silicon controlledrectifier 76.

The voltage divider network 71 is connected to the collector of thephototransistor 91 of the optocoupler 90. A coil 77 connects the emitterof phototransistor 91 to the gate of the thyristor 76. A pull downresistor 78 and a capacitor 79 are connected to the gate of thethyristor 76.

The secondary circuit 80 comprises resistor 81 and 82 forming a voltagedivider network 83. The voltage divider network 83 is connected to lightemitting diodes 92 and 93 within the optocoupler 90. A connector 84connects the light emitting diodes 92 and 93 to the shield 48surrounding the second wires 42. A connector 85 connects the shield 48surrounding the second wire 42 to the shield 47 surrounding the firstsecond wire 41.

An optional test circuit 100 may be included for testing the circuit 10.The optional test circuit 100 comprises resistor 101 connected to thewire 42 of the wire assembly 40. A momentary switch 102 connects theresistor 101 to the shield 47 surrounding the first second wire 41through a conductor 103.

FIG. 13 is a diagram of the circuit 10 of FIG. 12 connected to the powersource 15. Power is applied to the circuit 10 by inserting the first andsecond terminals 21 and 22 extending from the housing 20 into theelectrical receptacle 17 shown in FIG. 1. Upon the application of power,conventional current flows from diode 68 through the solenoid coil 58 tothe voltage divider network 71. The diode 68 in combination withsolenoid coil 58 provides a direct current (DC) voltage for the primarycircuit 70.

The conductor 69 applies power to the voltage divider network 71 and tothe anode of the thyristor 76. The capacitor 75 assists in reducingalternating current (AC) voltage ripple within the voltage dividernetwork 71. The voltage divider network 71 provides operating voltage tothe collector of phototransistor 91. The total resistance of resistors72 and 73 of the voltage divider network 71 is selected to establish aminor conventional current flow through the solenoid coil 58. The minorvoltage through the solenoid coil 58 is insufficient to actuate thedisconnect switch 50.

The voltage divider circuit 83 of the secondary circuit 80 providesoperating voltage to the light emitting diodes 92 and 93. The lightemitting diodes 92 and 93 are connected through conductor 84 to theshield 48 surrounding the second wire 42 and connected through conductor85 to the shield 47 surrounding the first wire 41.

In the absence of a leakage current between the first wire 41 and thesurrounding shield 47 and the absence of a leakage current between thesecond wire 42 and the surrounding shield 48, the light emitting diodes92 and 93 will not illuminate the phototransistor 91 of the optocoupler90. The absence of illumination of the phototransistor 91 will keep thegate of the thyristor 76 in a low voltage condition. The pull downresistor 78 and capacitor 79 in combination with the coil 77 preventsinadvertent actuation of the thyristor 76 by electrical transients. Aslong as thyristor 76 is in a non-conductive condition, the disconnectswitch 50 remains in the closed or reset condition.

FIG. 14 is the circuit 10 of FIG. 13 with a leakage current R1established between the first wire 41 and the shield 47. Preferably, thevoltage divider circuit 83 establishes a threshold for the leakagecurrent R1 to be less than 0.001 amperes but it should be understoodthat the threshold for the leakage current R1 may be established at anysuitable value. When a positive half-cycle of AC voltage is present onthe first wire 41, conventional current flows from the first wire 41through the leakage resistor R1 through light emitting diode 92 to thevoltage divider circuit 83. When a negative half-cycle of AC voltage ispresent on the first wire 41, conventional current flows from thevoltage divider circuit 83 through light emitting diode 93 to the firstwire 41 through the leakage resistor R1.

If a leakage current (not shown) develops between the second wire 42 andthe shield 48, the circuit 10 undergoes the following current flows.When a positive half-cycle of AC voltage is present on the first wire41, conventional current flows from the voltage divider circuit 83through light emitting diode 93 to the second wire 42 through theleakage resistor R. When a negative half-cycle of AC voltage is presenton the first wire 41, conventional current flows from the second wire 42through the leakage resistor R through light emitting diode 92 to thevoltage divider circuit 83.

The leakage current between the first wire 41 and the shield 47 isconducted through one of the light emitting diodes 92 and 93. Theconduction of the leakage current through one of the light emittingdiodes 92 and 93 illuminates the phototransistor 91. Upon illumination,of the phototransistor 91, phototransistor 91 conducts conventionalcurrent from the collector to the emitter. Upon the conduction of thephototransistor 91, the charge on capacitor 75 flows throughphototransistor 91 raising the voltage on the gate of the thyristor 76to institute conduction of the thyristor 76. The conduction of thethyristor 76 results in a major conventional current flow through thesolenoid coil 58. The major conventional current flow through thesolenoid coil 58 actuates the plunger 59 to open the disconnect switch50 as shown in FIG. 9.

FIG. 15 is the circuit 10 of FIG. 14 illustrating the disconnection ofthe power source 15 from the load 30 upon the opening of the disconnectswitch 50. The opening of the disconnect switch 50 completely isolatesthe power source 15 from the load 30. The optical coupling between thephototransistor 91 and the light emitting diodes 92 and 93 completelyelectrically isolates the primary circuit 70 from the secondary circuit80.

FIG. 16 is the circuit 10 of FIG. 12 illustrating the operation of theoptional test circuit 100. A momentary depression of momentary switch102 causes conventional current flow to flow from the second wire 42through resistor 101 and conductor 103 to the shield 47. Since theshield numeral 47 is connected to the shield 48 by the connector 85, theclosing of the switch 102 creates a current between the second wire 42and the shield 48.

The current between the second wire 42 and the shield 48 is conductedthrough the one of the light emitting diodes 92 and 93 to illuminate thephototransistor 91. The conduction of phototransistor 91 institutesconduction of the thyristor 76 resulting in a major conventional currentflow through the solenoid coil 58. The major conventional current flowthrough the solenoid coil 58 actuates the plunger 59 to open thedisconnect switch 50 as shown in FIG. 9. The circuit 10 may be return toclosed and reset position by the depression of the reset button 102.

FIG. 17 is a circuit diagram of a second embodiment of the circuit 110of FIGS. 1-4. Similar parts are labeled with similar reference numeralsraised by the number 100. In this example, the electrical power source115 is shown as a conventional 220 volt alternating current (AC) powersource. Although the electrical power source 115 has been shown asconventional 220 volt alternating current (AC) power source, it shouldbe appreciated by those skilled in the art that the present inventionmay be adapted to virtually any type of power source.

In this example, a voltage dropping resistor 167 is inserted in seriesbetween the first wire 141 and diode 168. In this example, the voltagedivider network 171 is formed from resistor 172 and zener diode 173. Thecombination of the voltage dropping resistor 167 and the voltage dividernetwork 171 comprising resistor 172 and zener diode 173 provides a minorconventional current through solenoid coil 158 to supply a collectorvoltage for the phototransistor 191. The operation of the secondembodiment of the circuit 110 is essentially identical to the operationof the first embodiment shown in FIGS. 3-16.

FIG. 18 is a circuit diagram of a third embodiment of the circuit 210 ofFIGS. 1-4. In this embodiment of the invention the disconnect switch 250is interposed between the source 215 and the load 230. The primarycircuit 270 received operating power from a primary side or source sideof the disconnect switch 250 by conductors 271 and 272. The secondarycircuit 280 received operating power from a secondary side or load sideof the disconnect switch 250 by conductors 281 and 282. The secondarycircuit 280 is optically connected to the primary circuit 270 by theoptocoupler 290.

In this example a conductor 292 connects a sensor 294 to the secondarycircuit 280. The sensor 294 senses any leakage from either the first orthe second wires 241 and 242. The sensor 294 may be the ground wirenormally included in a conventional 110 volt alternating current powercord.

When the sensor 294 senses a leakage from either the first or the secondwires 241 and 242, the secondary circuit 280 optically actuates theprimary circuit 270 for opening the disconnect switch 250. Thedisconnect switch 250 may be any type of appropriate switch fordisconnecting the source 215 from the load 230 including electrical,electronic or electrical-mechanical switches.

FIG. 19 is a circuit diagram of a fourth embodiment of the circuit 310of FIGS. 1-4. In this embodiment of the invention the disconnect switch350 is interposed between the source 315 and the load 330. The primarycircuit 370 received operating power from a primary side or source sideof the disconnect switch 350 by conductors 371 and 372. The secondarycircuit 380 received operating power from a secondary side or load sideof the disconnect switch 350 by conductors 381 and 382. The secondarycircuit 380 is optically connected to the primary circuit 370 by theoptocoupler 390.

In this example a conductor 392 connects a sensor 394 to the secondarycircuit 380. The sensor 394 senses any leakage from the load 330. Whenthe sensor 394 senses a leakage from the load 330, the secondary circuit380 optically actuates the primary circuit 370 for opening thedisconnect switch 350.

FIG. 20 is a circuit diagram of a fifth embodiment of the circuit 410 ofFIGS. 1-4. Similar parts are labeled with similar reference numeralsraised by the number 400. In this embodiment, the primary circuit 470and the secondary circuit 480 of the circuit are located on thesecondary side of the switch 450. The secondary side of switch 450 islocated between the switch 450 and the load 430. The remainder of thefifth embodiment of the circuit 410 is essentially identical to thefirst embodiment of the circuit 10 shown in FIGS. 3-16.

This circuit 410 is may be used where it is desirable to have theprimary circuit 470 and the secondary circuit 480 disconnected from thepower source 415 upon the opening of the switch 450. The operation ofthe fifth embodiment of the circuit 110 is similar to the operation ofthe first embodiment shown in FIGS. 3-16.

The disconnect switch 450 defines a primary side 450P connected to thepower source 415 and a secondary side 450S connected to the load 430.The normally open disconnect switched 450 is mechanically closed toconnect the first and second terminals 421 and 422 to the first andsecond wires 441 and 442 of the wire assembly 440.

Upon the application of power, conventional current flows from thesecondary side 450S of the disconnect switch 450 through the solenoidcoil 458 to the voltage divider network 471 to provide a direct current(DC) voltage for the primary circuit 470 and to the collector ofphototransistor 491 of the optocoupler 490.

The voltage divider circuit 483 of the secondary circuit 480 isconnected to the secondary side 4505 of the disconnect switch 450 toprovide operating voltage to the light emitting diodes 492 and 493. Thelight emitting diodes 492 and 493 are connected through conductor 484 tothe shields 447 and 448.

In the absence of any leakage current between the either of the firstand second wires 441 and 442 the respective shields 447 and 448, thelight emitting diodes 492 and 493 will not illuminate thephototransistor 491 of the optocoupler 490. The thyristor 476 ismaintained in a non-conductive condition, the disconnect switch 450remains in the closed or reset condition.

In the presence of the leakage current between the either o ft he firstand second wires 441 and 442 and the respective shields 447 and 448, thelight emitting diodes 492 and 493 will illuminate the phototransistor491 of the optocoupler 490. The phototransistor 491 of the optocoupler490 causes conduction of the thyristor 476 to open the disconnect switch450. The opening of the disconnect switch 450 completely isolates thepower source 415 from the load 430.

In contrast to the previous embodiments set forth in FIGS. 1-19, uponthe opening of the disconnect switch 450, both the primary circuit 470and the secondary circuit 480 are disconnected from the power source415. Upon the disconnection of the primary circuit 470 from the powersource 415, the primary circuit 470 is incapable of electricallyresetting or closing the disconnect switch 450.

FIG. 21 is a circuit diagram of a sixth embodiment of the circuit 510 ofFIGS. 1-4. In this embodiment of the invention the disconnect switch 550is interposed between the source 515 and the load 530. The primarycircuit 570 received operating power from a secondary side or load sideof the disconnect switch 550 by conductors 571 and 572. The secondarycircuit 580 received operating power from a secondary side or load sideof the disconnect switch 550 by conductors 581 and 582. The secondarycircuit 580 is optically connected to the primary circuit 570 by theoptocoupler 590.

In this example a conductor 592 connects a sensor 594 to the secondarycircuit 580. The sensor 594 senses the leakage from either the first orthe second wires 541 and 542. The sensor 594 may be the ground wirenormally included in a conventional 110 volt alternating current powercord.

When the sensor 594 senses a leakage from either the first or the secondwires 541 and 542, the secondary circuit 580 optically actuates theprimary circuit 570 for opening the disconnect switch 550. Thedisconnect switch 550 may be any type of appropriate switch fordisconnecting the source 515 from the load 530 including electrical,electronic or electrical-mechanical switches.

FIG. 22 is a circuit diagram of a seventh embodiment of the circuit 610of FIGS. 1-4. In this embodiment of the invention the disconnect switch650 is interposed between the source 615 and the load 630. The primarycircuit 670 received operating power from a secondary side or load sideof the disconnect switch 650 by conductors 671 and 672. The secondarycircuit 680 received operating power from a secondary side or load sideof the disconnect switch 650 by conductors 681 and 682. The secondarycircuit 680 is optically connected to the primary circuit 670 by theoptocoupler 690.

In this example a conductor 692 connects a sensor 694 to the secondarycircuit 680. The sensor 694 senses the leakage from the load 630. Whenthe sensor 694 senses the leakage from the load 630, the secondarycircuit 680 optically actuates the primary circuit 670 for opening thedisconnect switch 650.

The present invention has been shown in a preferred form employed withina circuit contained within a housing 20 fashioned in the form of anelectrical plug. However, it should be understood that the presentinvention may be applied to of various types of protection devices forprotecting all types of electrical cords, electrical transmission linesand electrical circuits. Furthermore, the present invention has beenshown with an air conditioning unit 32 as the load 30 but it should beunderstood that the circuit 10 of the present invention is suitable foruse with a large variety of power sources and load as should be apparentto those skilled in the art.

The present disclosure includes that contained in the appended claims aswell as that of the foregoing description. Although this invention hasbeen described in its preferred form with a certain degree ofparticularity, it is understood that the present disclosure of thepreferred form has been made only by way of example and that numerouschanges in the details of construction and the combination andarrangement of parts may be resorted to without departing from thespirit and scope of the invention.

1. A circuit for disconnecting a power source upon the detection of aleakage current from one of a first and a second wire connected to thepower source, comprising: a disconnect switch interposed within thefirst and second wires connected to the power source; said disconnectswitch defining a primary side and a secondary side of said disconnectswitch with said primary side located adjacent to said power source; aprimary circuit including a photoconductive switch located on saidprimary side of said disconnect switch for controlling said disconnectswitch; a secondary circuit located on said secondary side of saiddisconnect switch; said secondary circuit including a sensing conductorlocated adjacent to the first and second wires for sensing a leakagecurrent from the first and second wires; said secondary circuitcomprising a light emitting device connected in series with a resistorbetween said sensing conductor and both of the first and second wiresfor actuating said light emitting device upon a leakage current flowbetween said sensing conductor and one of the first and second wires;and said photoconductive switch being optically coupled to said lightemitting device for opening said disconnect switch upon said secondarycircuit sensing a leakage current between said sensing conductor and oneof the first and second wires.
 2. A circuit as set forth in claim 1,wherein said sensing conductor includes a shield sensing conductorlocated about at least one of the first and second wires connected tothe power source.
 3. A circuit as set forth in claim 1, wherein saidsensing conductor includes a shield sensing conductor located about bothof the first and second wires connected to the power source.
 4. Acircuit as set forth in claim 1, wherein said photoconductive switch andsaid light emitting device completely electrically isolates the powersource and completely electrically isolates said primary circuit fromsecondary circuit upon the opening of said disconnect switch.
 5. Acircuit as set forth in claim 1, wherein said light emitting devicecomprises a light emitting diode.
 6. A circuit as set forth in claim 1,wherein said disconnect switch includes a normally open solenoidoperated switch; a mechanical latch mechanism for maintaining saiddisconnect switch in a closed condition; and said primary circuitoperating said mechanical latch mechanism for opening said solenoidoperated switch upon said secondary circuit sensing a leakage currentfrom one of the first and second wires.
 7. A circuit for disconnecting apower source upon the detection of a leakage current from one of a firstand second wire connected to the power source, comprising: a disconnectswitch interposed within the first and second wires connected to thepower source; said disconnect switch defining a primary side and asecondary side of said disconnect switch with said primary side locatedadjacent to said power source; a primary circuit including aphotoconductive switch located on said primary side of said disconnectswitch for controlling said disconnect switch; a secondary circuitlocated on said secondary side of said disconnect switch; said secondarycircuit including a sensing conductor located adjacent to the first andsecond wires for sensing a leakage current from the first and secondwires; a secondary circuit comprising a non-reactive divider circuitconnected between the first and second wires for providing a dividernode between the first and second wires; a light emitting device locatedin said secondary circuit and connected between said divider node andsaid sensing conductor for illuminating said light emitting device upona leakage current flowing between said sensing conductor and one of thefirst and second wires; and said photoconductive switch being opticallycoupled to said light emitting device for opening said disconnect switchupon said secondary circuit sensing a leakage current between saidsensing conductor and one of the first and second wires.
 8. A circuitfor disconnecting a power source upon the detection of a leakage currentfrom one of a first and second wire connected to the power source,comprising: a disconnect switch interposed within the first and secondwires connected to the power source; said disconnect switch defining aprimary side and a secondary side of said disconnect switch with saidprimary side located adjacent to said power source; a primary circuitincluding a photoconductive switch located on said primary side of saiddisconnect switch for controlling said disconnect switch; a secondarycircuit located on said secondary side of said disconnect switch; saidsecondary circuit including a sensing conductor located adjacent to thefirst and second wires for sensing a leakage current from the first andsecond wires; a secondary circuit comprising a resistive voltage dividercircuit connected between the first and second wires for providing avoltage divider node between the first and second wires; a lightemitting device located in said secondary circuit and connected betweensaid voltage divider node and said sensing conductor for illuminatingsaid light emitting device upon a leakage current flowing between saidsensing conductor and one of the first and second wires; and saidphotoconductive switch being optically coupled to said light emittingdevice for opening said disconnect switch upon said secondary circuitsensing a leakage current between said sensing conductor and one of thefirst and second wires.
 9. A circuit for disconnecting a power sourceupon the detection of a leakage current from one of a first and secondwire connected to the power source, comprising: a disconnect switchinterposed within the first and second wires connected to the powersource; said disconnect switch defining a primary side and a secondaryside of said disconnect switch with said primary side located adjacentto said power source; said disconnect switch comprising a disconnectswitch coil for changing said disconnect switch from a closed positionconnecting said power source to the first and second wires to an openposition for disconnecting power source from the first and second wiresupon a threshold current flow through said disconnect switch coil; aprimary circuit located on said primary side of said disconnect switchfor controlling said disconnect switch; said primary circuit comprisinga driver switch connected in series with said disconnect switch coilacross the power source for providing said threshold current flowthrough said disconnect switch coil upon actuation of said driverswitch; a secondary circuit located on said secondary side of saiddisconnect switch including a sensing conductor located adjacent to thefirst and second wires; said secondary circuit having a light emittingdevice connected for illuminating said light emitting device upon aleakage current flowing between said sensing conductor and one of thefirst and second wires; a photoconductive switch located in said primarycircuit and optically coupled to said light emitting device located insaid secondary circuit; a resistor connected in series with said coilacross the power source for providing a reduced current flow throughsaid coil below said threshold current required to open said disconnectswitch to supply an operating voltage to said photoconductive switch;and said photoconductive switch connected to said driver switch foractuating said driver switch upon said secondary circuit sensing aleakage current in said sensing conductor to open said disconnect switchfor electrically disconnecting the power source from the first andsecond wires.
 10. A circuit as set forth in claim 8, wherein said driverswitch of said primary circuit includes a silicon controlled rectifierfor opening said disconnect switch upon said secondary circuit sensing aleakage current from the wire.
 11. A circuit for disconnecting a powersource upon the detection of a leakage current from one of a first andsecond wire connected to the power source, comprising: a disconnectswitch interposed within the first and second wires connected to thepower source; said disconnect switch defining a primary side and asecondary side of said disconnect switch with said primary side locatedadjacent to said power source; said disconnect switch comprising adisconnect switch coil for changing said disconnect switch from a closedposition connecting said power source to the first and second wires toan open position for disconnecting power source from the first andsecond wires upon a threshold current flow through said disconnectswitch coil; a primary circuit located on said primary side of saiddisconnect switch for controlling said disconnect switch; said primarycircuit comprising a driver switch connected in series with saiddisconnect switch coil across the power source for providing saidthreshold current flow through said disconnect switch coil uponactuation of said driver switch; a secondary circuit located on saidsecondary side of said disconnect switch including a sensing conductorlocated adjacent to the first and second wires; said secondary circuithaving a light emitting device connected for illuminating said lightemitting device upon a leakage current flowing between said sensingconductor and one of the first and second wires; a photoconductiveswitch located in said primary circuit and optically coupled to saidlight emitting device located in said secondary circuit; a resistorconnected in series with said coil across the power source and inparallel with said driver switch for providing a reduced current flowthrough said coil below said threshold current required to open saiddisconnect switch to supply an operating voltage to said photoconductiveswitch; and said photoconductive switch connected to said driver switchfor actuating said driver switch upon said secondary circuit sensing aleakage current in said sensing conductor to open said disconnect switchfor electrically disconnecting the power source from the wire.
 12. Acircuit for disconnecting a power source upon the detection of a leakagecurrent from one of a first and second wire connected to the powersource, comprising: a disconnect switch interposed within the first andsecond wires connected to the power source; said disconnect switchdefining a primary side and a secondary side of said disconnect switchwith said primary side located adjacent to said power source; saiddisconnect switch comprising a disconnect switch coil for changing saiddisconnect switch from a closed position connecting said power source tothe first and second wires to an open position for disconnecting powersource from the first and second wires upon a threshold current flowthrough said disconnect switch coil; a primary circuit located on saidprimary side of said disconnect switch for controlling said disconnectswitch; said primary circuit comprising a driver switch connected inseries with said disconnect switch coil across the power source forproviding said threshold current flow through said disconnect switchcoil upon actuation of said driver switch; a diode connected in serieswith said disconnect switch coil across the power source; a secondarycircuit located on said secondary side of said disconnect switchincluding a sensing conductor located adjacent to the first and secondwires; said secondary circuit having a light emitting device connectedfor illuminating said light emitting device upon a leakage currentflowing between said sensing conductor and one of the first and secondwires; a photoconductive switch located in said primary circuit andoptically coupled to said light emitting device located in saidsecondary circuit; a resistor connected in series with said coil acrossthe power source and in parallel with said driver switch for providing areduced current flow through said coil below said threshold currentrequired to open said disconnect switch to supply an operating voltageto said photoconductive switch; and said photoconductive switchconnected to said driver switch for actuating said driver switch uponsaid secondary circuit sensing a leakage current in said sensingconductor to open said disconnect switch for electrically disconnectingthe power source from the wire.
 13. A circuit for disconnecting a powersource upon the detection of a leakage current from one of a first and asecond wire connected to the power source, comprising: a disconnectswitch interposed within the first and second wires connected to thepower source; said disconnect switch defining a primary side and asecondary side of said disconnect switch with said primary side locatedadjacent to said power source; a primary circuit including aphotoconductive switch located on said primary side of said disconnectswitch for controlling said disconnect switch; said primary circuitcomprising a driver switch connected in series with said disconnectswitch coil across the power source for providing said threshold currentflow through said disconnect switch coil upon actuation of said driverswitch; a diode connected in series with said disconnect switch coilacross the power source; a resistor connected in series with saiddisconnect switch coil across the power source and in parallel with saiddriver switch for providing reduced current flow through said coil belowsaid threshold current required to open said disconnect switch to supplyan operating voltage to said photoconductive switch; a secondary circuitlocated on said secondary side of said disconnect switch; said secondarycircuit including a sensing conductor located adjacent to the first andsecond wires for sensing a leakage current from the first and secondwires said secondary circuit comprising a non-reactive divider circuitconnected between the first and second wires for providing a dividernode between the first and second wires; a light emitting device locatedin said secondary circuit and connected between said divider node andsaid sensing conductor for illuminating said light emitting device upona leakage current flowing between said sensing conductor and one of thefirst and second wires; and said photoconductive switch being opticallycoupled to said light emitting device for opening said disconnect switchupon said secondary circuit sensing a leakage current in said sensingconductor for completely electrically isolating said primary circuitfrom secondary circuit upon the opening of said disconnect switch.